Offspring are also more likely to suffer from anxiety and depression, according to study led by Hanan El Marroun

Children born to mothers who smoke during pregnancy have smaller brains and are more likely to suffer from anxiety and depression, according to research just published.

The findings published by Neuropsychopharmacology magazine last night in New York and London, followed research into more than 200 six to eight-year-old Dutch children.

The study found that tobacco affects the development of the foetus’s nervous system, partly because it interferes with the growth of neurons and partly because smoking narrows the blood vessels of the foetus.

Half of the mothers selected for the research smoked and half did not but the brains of the children of those who continued smoking were significantly smaller up to eight years later.

Equally, they showed greater levels of anxiety and depression because their brains’ superior frontal cortex, which regulates mood swings, had developed more poorly.

The study did “not demonstrate” a clear link between the number of cigarettes smoked, which varied from between just one a day to more than nine, but the length of time a mother continued to smoke was critical. Seventeen smokers quit when told that they were pregnant, though the research found that children were unaffected by their mothers’ habits if they quit early enough.

“Importantly, brain development in offspring of mothers who quit smoking during pregnancy resembled that of [mothers who never smoked] with no smaller brain volumes and no thinning of the cortex,” said the research led by Hanan El Marroun at Rotterdam’s Erasmus University Medical Centre.

The children selected for the research in September 2009 were subjected to MRI scans: “Children exposed to tobacco throughout pregnancy have smaller total brain volumes and smaller cortical grey matter volumes.

“Continued prenatal tobacco exposure was associated with cortical thinning, primarily in the superior frontal, superior parietal and precentral cortices. These children also demonstrated increased scores of affective problems,” according to the findings.

Responding to the research, Dr Simon Newell of the Royal College of Paediatrics and Child Health in London said: “What was striking about this study was the alarming effect smoking had on the brain over six years later.”